Q960E超高强钢焊接接头组织和性能研究

目的 对Q960E超高强钢的焊接工艺进行研究以获得高强高韧的焊接接头。方法 选择超高强钢Q960E作为母材、FK1000ER120S–G焊丝作为填充材料进行MAG焊，采用改变焊接电流的方式来研究焊接热输入对焊接接头组织和性能的影响。结果 当焊接电流为155~230 A时，均获得了全焊透无明显缺陷的焊缝。随着焊接热输入的增大，焊接接头中各亚区宽度增大，其中焊缝区变化最为显著，在最小热输入条件下焊缝宽度为3.98 mm，在最大热输入条件下焊缝宽度增至5.53 mm。对焊接接头进行组织分析发现，焊缝组织主要为针状铁素体和板条马氏体;完全相变区组织主要为板条马氏体;未完全相变区组织主要为回火马氏体和部分重结晶形成的马氏体。硬度测试表明，在热影响区的回火区发生了软化现象，最低硬度仅为290HV;在完全相变区发生了硬化现象，硬度最大值可达500HV。在不同热输入条件下，焊接接头各亚区硬度变化趋势一致，焊接接头抗拉强度为995~1 076 MPa，拉伸试验均断裂在热影响区，断后伸长率为9.33%~10.21%，断裂时存在颈缩现象，为韧性断裂。随着热输入的增加，粗晶区马氏体板条束宽度增大，未完全相变区马氏体含量上升。结论 在所选焊接工艺窗口内焊接均能获得高强高韧的焊接接头。

Microstructure and Properties of Welded Joints of Q960E Ultra-high Strength Steel

The work aims to study the welding technology of steel to obtain high strength and high toughness welded joint. Ultra-high strength steel Q960E was selected as the base material and FK1000ER120S-G welding wire as the filler for MAG welding. The effect of welding heat input on the microstructure and properties of welded joints was studied by changing the welding current. When the welding current was 155-230 A, a weld with full penetration but without obvious defects was obtained. With the increase of welding heat input, the width of each sub-zone in the welded joint increased, and the weld zone had the most significant change. The width of the weld was 3.98 mm at the minimum heat input and increased to 5.53 mm at the maximum heat input. The microstructure analysis of welded joint showed that the weld microstructure was mainly acicular ferrite and lath martensite. The microstructure of the complete phase change zone was mainly lath martensite. The microstructure of the incomplete phase change zone was mainly tempered martensite and some martensite formed after recrystallization. The hardness test showed that softening occurred in the tempered zone of the heat affected zone, and the lowest hardness was only 290HV. Hardening occurred in the complete phase change zone, with a maximum value of 500HV. Under different heat input, the variation trend of hardness in each sub-zone of welded joint was consistent. The tensile strength of welded joints was between 995-1 076 MPa, and the fracture was in the heat affected zone. The elongation after fracture was between 9.33% and 10.21%, and there was a necking phenomenon at fracture, which was a ductile fracture. With the increase of heat input, the width of martensitic slats in the coarse-grained zone increased, while the martensite content in the incomplete phase change zone increased. High strength and high toughness welded joints can be obtained by welding in the selected welding process window.